package tool;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.List;

public class GenerateAst {
  private static void defineType(
      PrintWriter writer,
      String baseName,
      String className,
      String fieldList
      )
  {
    writer.println("  static class " + className + " extends " + baseName + " {");
    writer.println("    " + className + "(" + fieldList + ") {");

    String[] fields = fieldList.split(", ");
    for (String field : fields) {
      String name = field.split(" ")[1];
      writer.println("      this." + name + " = " + name + ";");
    }

    writer.println("    }");

    writer.println();
    writer.println("    @Override");
    writer.println("    <R> R accept(Visitor<R> visitor) {");
    writer.println("      return visitor.visit" + className + baseName + "(this);");
    writer.println("    }");

    writer.println();
    for (String field : fields) {
      writer.println("    final " + field + ";");
    }

    writer.println("  }");
  }

  private static void defineVisitor(
      PrintWriter writer,
      String baseName,
      List<String> types
      )
  {
    writer.println("  interface Visitor<R> {");

    for (String type : types) {
      String typeName = type.split(":")[0].trim();
      writer.println("    R visit" + typeName + baseName + "(" + 
          typeName + " " + baseName.toLowerCase() + ");");
    }

    writer.println("  }");
  }

  private static void defineAst(
      String outputDir,
      String baseName,
      List<String> types
      ) throws IOException
  {
    String path = outputDir + "/" + baseName + ".java";
    PrintWriter writer = new PrintWriter(path, "UTF-8");

    writer.println("package lox;");
    writer.println();
    writer.println("import java.util.List;");
    writer.println();
    writer.println("abstract class " + baseName + " {");

    defineVisitor(writer, baseName, types);

    for (String type : types) {
      String className = type.split(":")[0].trim();
      String fields = type.split(":")[1].trim();
      defineType(writer, baseName, className, fields);
    }

    writer.println();
    writer.println("  abstract <R> R accept(Visitor<R> visitor);");

    writer.println("}");
    writer.close();
  }

  public static void main(String[] args) throws IOException
  {
    if (args.length != 1) {
      System.err.println("Usage: gnerate_ast <output directory>");
      System.exit(64);
    }
    String outputDir = args[0];
    defineAst(outputDir, "Expr", Arrays.asList(
          "Assign    : Token name, Expr value",
          "Binary    : Expr left, Token operator, Expr right",
          "Call      : Expr callee, Token paren, List<Expr> arguments",
          "Get       : Expr object, Token name",
          "Grouping  : Expr expression",
          "Literal   : Object value",
          "Logical   : Expr left, Token operator, Expr right",
          "Set       : Expr object, Token name, Expr value",
          "Super     : Token keyword, Token method",
          "This      : Token keyword",
          "Unary     : Token operator, Expr right",
          "Variable  : Token name"
    ));

    defineAst(outputDir, "Stmt", Arrays.asList(
          "Block      : List<Stmt> statements",
          "Class      : Token name, Expr.Variable superclass, List<Stmt.Function> methods",
          "Expression : Expr expression",
          "Function   : Token name, List<Token> params, List<Stmt> body",
          "If         : Expr condition, Stmt thenBranch, Stmt elseBranch",
          "Print      : Expr expression",
          "Return     : Token keyword, Expr value",
          "Var        : Token name, Expr initializer",
          "While      : Expr condition, Stmt body"
    ));
  }
}
